The present invention relates to torsion spring counterbalancing mechanisms for compensating the weight of roll-up doors. More particularly, the present invention relates to a faster, safer, and easier apparatus and method for loading the coil torsion spring of roll-up doors.
Roll-up doors, commonly referred to as overhead garage doors, typically use counterbalancing mechanisms incorporating coil springs placed under a rotational or torsion force to apply a lifting force to the door. The springs are concentrically positioned about a shaft rotatably mounted on fixed supports. The shaft carries hubs accommodating cables. The cables are attached to the door so that when the hubs are rotated, a lifting force will be applied to the door. The lifting force is transmitted to the hubs via the shaft by the torsion springs.
Conventional torsion springs used in door counterbalancing mechanisms have adjacent coils that engage or abut one another when the spring is in its normal unwound resting state. There is no gap between adjacent coils. During the winding process of a torsion coil spring, friction forces are generated between adjacent coils of the spring.
Conventional coil torsion springs having abutting coils do not provide for growth and contraction of the spring during the initial winding of the spring unless one end remains unfixed, nor do such springs provide for the springs unwinding aid winding after installation of the roll-up door. Carper et al. U.S. Pat. No. 5,632,063 discloses a sliding cone to anchor an end of the torsion spring to the shaft to allow the spring to elongate and contract as the roll-up door opens and closes. This requires a modification of the end cone and rod as the cone must axially move on the rod. Conventional shafts and end cones for the torsion coil spring cannot be used in the Carper et al. door counterbalancing system.
Generally, a coil torsion spring must be twisted to load the spring or place the spring under torsion force. Heretofore, winding bars or steel rods have been used to turn the cone fitting attached to the spring to load the spring. A limited amount of force can be applied to the spring since twisting the collar is a manual operation. The procedure requires a considerable amount of time and can be dangerous as the spring is loaded with considerable force. Worm gear power transmission units have been incorporated in door counterbalancing mechanisms. Examples of this type of power transmission unit to wind or twist torsion springs are disclosed by Votroubek et al. U.S. Pat. No. 3,921,761 (which is incorporated herein by reference). Votroubek et al. recognizes the danger involved in winding and unwinding a garage door torsion spring and attempts to address this problem. Votroubek et al. utilizes a tool with a self-locking worm drive gear and worm wheel which can be put into place about the torsion shaft to effect a gripping of an end collar for connecting the spring to the torsion shaft. After the collar is gripped, the end collar is released from the shaft for movement along the rotation about the torsion shaft. In Votroubek et al., the tool is mounted on the torsion shaft and blocked against rotation about the torsion shaft in a manner to allow the tool to move axially on the torsion shaft, as the spring is wound, to accommodate the growth of the spring during winding. In a double spring configuration using the Votroubek et al. tool, the springs would be wound and unwound separately with the tool being used to wind the outer-end of each spring.
While the Votroubek et al. tool lessens danger, as compared to the conventional use of a lever bar for winding or unwinding a spring, the spring end is still held by a tool which is separate from the hardware of the counterbalancing mechanism and which must be assembled and disassembled to the counterbalancing mechanism for each winding, unwinding or adjustment of a torsion spring. This tool also must be securely blocked against rotation as a whole about the axis of the torsion rod each time a spring end is to be wound or unwound. Further, during the use of the tool, as in the case of using a lever bar, the door being counterbalanced is placed in a locked position until the winding operation has been completed and the freed end cones or members of the spring are resecured to the torsion shaft. With the door locked, the setting of the proper spring forces in the torsion spring or springs is done with the use of charts and spring characteristic specifications. When working in this manner, it is more difficult to adjust to the proper counterbalancing forces, as is true of all the present conventional methods known to applicant, for setting the torsion in a torsion counterbalancing mechanism for a garage door.
Mullet U.S. Pat. No. 5,419,010 (which is incorporated herein by reference) discloses a counterbalancing mechanism for sectional doors that features a duel shaft system. The counterbalancing mechanism of Mullet has a drive tube 30 extending between a pair of drums and being non-rotatably affixed thereto, a coil spring 80 positioned interiorly of the drive tube, the coil spring having one end 82 non-rotatably affixed to the drive tube and the other end 81 non-rotatably affixed to the shaft, and a tension adjusting mechanism. The counterbalancing system disclosed in Mullet is more complicated to install and maintain because the duel shaft system uses non-standard components, thereby creating complicated maintenance and repairs to the torsion spring assembly.
Carper et al. U.S. Pat. No. 5,632,063 and Carper et al. U.S. Pat. No. 5,636,678 (which are incorporated herein by reference) disclose an overhead door apparatus utilizing a torsion spring counterbalancing mechanism. The counterbalancing mechanism includes a worm drive ring-shaped gear winding mechanism for setting the appropriate torque or number of winds in the spring. The torsion spring disclosed in the Carper et al. patents has gaps between adjacent coils making it a non-standard torsion spring and spring assembly. Additionally, the torsion spring counterbalancing mechanism of the Carper et al. patents require specialty anchor and winding cones and specialty drums which are not off-the-shelf components. Thus, the need exists for a counterbalancing mechanism which permits simpler installation and maintenance and uses standard off-the-shelf components.
The present invention eliminates the dangers of prior art mechanisms relating to torsion spring counterbalancing, simplifies the installation and maintenance with an accompanying savings in time and labor, improves the counterbalancing system performance, and utilizes off-the-shelf drums and cones.